The present invention relates to fuel injection and specifically to the ability to control flow rates to and from an intensifier piston and the ability to reset the intensifier piston quickly.
Reducing emissions is a top priority for today""s engine manufacturers. As the government continues to tighten emission requirements, manufacturers must find new ways to reduce engine emissions while still providing powerful, economic engine operation. One area that engine manufacturers have focused on is fuel injection.
Fuel injection plays a crucial role in the amount of emissions created during combustion. Numerous fuel injection variables, including fuel pressure, spray pattern, droplet size, number of injections and injection timing impact emissions. In order to properly control these parameters, fuel injectors have become more complicated and more precise. For example, one exemplary design of a fuel injector is a hydraulically actuated electronically controlled unit injector such as a Caterpillar HEUT(trademark) B unit injector. This unit injector uses actuation fluid to pressurize fuel for injection. Specifically, a control valve and spool valve control the timing of high pressure actuation fluid acting upon an intensifier piston. When high pressure actuation fluid acts on the intensifier piston, the hydraulic force overcomes a biasing force from a piston spring and moves the piston downward, also moving a plunger, which pressurizes fuel in the pressurization cavity for injection. When injection is over, the control valve allows the high pressure actuation fluid acting on the intensifier piston to vent. This allows a piston spring to push the intensifier piston and plunger back to their original position and reset them for the next injection
As emissions regulations have increased, injection strategies have become more complicated. For example, multiple injections, including pilots and posts, reduce emissions during combustion. However, it can be difficult for the Injector to cycle quickly enough to perform multiple injections during a single combustion event. In the hydraulically actuated electronically controlled unit injector described above, multiple injections can be performed by cycling the control valve but depending on the dwell time between injections and the desired injection profile, the intensifier piston may not properly reset between injections.
The present invention is intended to overcome one or more of the above problems.
A fuel injector comprises a high pressure actuation fluid source, a lower pressure drain, at least one fluid line selectively to one of high pressure actuation fluid source and lower pressure drain, an intensifier piston fluidly connected to the fluid line and a flow control valve. The flow control valve is in fluid communication with the fluid line and the intensifier piston and position to control the rate of flow to and from the intensifier piston. The flow control valve has a first flow rate in the first direction and a second flow rate in a second direction, the second rate being different from the first.
In another embodiment, a fuel injector comprises a high pressure actuation fluid source, a low pressure drain, flow control valve connected with the high pressure actuation fluid source and the low pressure drain and intensifier piston connected to flow control valve. The control flow valve controls the flow rate between the flow control valve and the intensifier piston and has a first flow rate in the first direction and a second flow rate in the second direction.
In another embodiment, a method of controlling intensifier piston comprises pressurizing the intensifier piston at a first flow rate and venting the intensifier piston at a second flow rate, wherein the second flow rate is different than the first flow rate.
In another embodiment of the present invention, a fuel injector comprises a high pressure actuation fluid source, low pressure drain, at least one fluid line selectively connected to one of the high pressure actuation fluid source and low pressure drain, and intensifier piston fluidly connected to the fluid line, and a flow control valve. The flow control is in fluid communication with the fluid line and the intensifier piston and position to control flow to and from the intensifier piston. Further, the flow control valve has a flow in a first direction and a second direction having a flow control valve having a flow restriction for flow in the first direction.
In another embodiment, fuel injector comprises high pressure actuation fluid source, low pressure drain, at least one fluid line, means for selectively connecting the fluid line to one of the high pressure actuation fluid source and low pressure drain, an intensifier piston fluidly connected to the fluid line, and a flow control. The flow control valve is in fluid communication with the fluid line and the intensifier piston and in position to control a rate of flow to and from the intensifier piston. Further, the flow control valve has a first flow rate in the first direction and a second flow rate, different from the first flow rate, in the second direction.